1. Field of the Invention
The present invention relates to a data storage disc unit and more particularly to a magnetic disc unit in which information is recorded or reproduced by making a magnetic head slidably contact the surfaces of a magnetic disc used as a magnetic recording medium.
2. Description of the Prior Art
In a magnetic disc unit of the type described, a magnetic disc is inserted or loaded into the magnetic disc unit in such a way that the upper surface of the magnetic disc faces upward, while the lower surface thereof faces downward. When the magnetic disc is inserted or loaded into the magnetic disc unit, it is automatically transported or displaced to its operative position by an automatic loading mechanism and then is securely clamped in position. Thereafter, a magnetic head slidably contacts the surfaces of the magnetic disc, so that information is recorded on or reproduced from the magnetic disc. However, if an operator erroneously inserts or loads a magnetic disc cassette in a wrong direction or upside down (which is referred to as "wrong insertion" in this specification), no recording or reproduction can be effected. Further, in this specification, the term "correct insertion" is used when the magnetic disc is correctly inserted.
The conventional magnetic disc unit of the type described, however, is not provided with means for detecting and alarming or otherwise indicating the wrong insertion of a magnetic disc. Therefore, in the case that no recording or reproduction can be effected, it may take some time until an operator notices that such a failure of recording or reproducing is caused by an erroneous insertion of a magnetic disc into a magnetic disc unit. Alternatively, the operator may misunderstand that the magnetic disc unit is out of order. Furthermore, the time elapsed until the wrong insertion is detected is wasted. When such wrong insertion is detected, one must operate the magnetic disc unit to discharge the inserted or loaded magnetic disc from the magnetic disc unit and then correctly insert or load the discharged magnetic disc. As clear from the above, the conventional magnetic disc unit of the type described above has a disadvantage in that its operability is not satisfactory.